<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
        div{
            width: 700px;
            height: 3px;
            padding: 40px;
            border: 1px solid #000;
            margin: 0 auto;
        }
        #username{
            font-size: 30px;
        }
    </style>
</head>
<body>
    <div>
        <form action="/check" method="get">
            输入昵称：
            <input type="text" id="username" name="username">
            <input type="submit" value="进入聊天室">
        </form>
    </div>
</body>
</html>